DESCRIPTION: Research Program: The candidate hopes to eventually improve the diagnosis and treatment of vestibular schwannomas. He hypothesizes that the specific mutations in the NF2 tumor suppressor gene account for the clinical findings in these patients. The goals are to define: 1) the specific mutations present in the NF2 tumor suppressor gene, 2) the relation of specific mutations to clinical manifestations, and 3) the relation of specific mutations to cellular proliferation fractions. Studies will be carried out in 150 archived schwannomas from his collaborator groups. Clinical data will be obtained from chart reviews and x-ray studies. In Specific Aim 1, heteroduplex analysis, single- strand conformation polymorphism (SSCP) and mRNA mutation analyses will be performed to determine types of mutations present. Flow cytometry and immunohistochemical analysis techniques will be used for measuring direct indicators of cellular proliferation in the tumor tissues.